Page 84, under
Zoom, third paragraph, last sentence:
{...} Finally, unless otherwise stated, models cannot embark upon, or voluntarily disembark from, a Zooming Flyer.
Also, for reference, page 85 under
Hover, second paragraph:
A Flyer with the Hover type must declare whether it is going to Zoom or Hover before it moves, and before any embarked models disembark, each Movement Phase.
So, if the 'Raven is Zooming, models cannot disembark from it until it has declared a Hover move. However you could declare a Hover, disembark the unit and then move the 'Raven in Hover (p81, Disembarking).
Looking at it (I've never really bothered before), Skies just seems to give a way of disembarking after moving more than 6" (say, a 12" Hover move), and doesn't explicitly say it overrides the "cannot disembark from a Zooming Flyer" part quoted above. But I've never seen it played that way, so I'm not sure on that I'll be honest.